The earliest recorded process of silver extraction occurred in first-century-bc China by an alchemist named Fang, who devised a secret procedure for boiling off mercury and leaving behind pure silver residue. After her husband tortured her in order to learn her secret, and as she was possibly suffering from mercury poisoning, she went insane. Ten centuries later a girl named Geng Xiansheng was summoned to the emperor’s palace to transform mercury and “snow” into silver. “She mastered the art of the yellow and white [alchemy],” wrote one historian of Geng, “with many other strong transformations, mysterious and incomprehensible.”